查看更多>>摘要：? 2022 Elsevier B.V.High-entropy alloys (HEAs) have received extensive interest owing to their unusual mechanical properties as a result of the extreme compositional complexity. Understanding the dislocation behavior under the influence of chemical disorder, especially chemical short-range ordering (SRO), which is commonly found in HEAs, is fundamental to the rational design of high-performance alloy systems. Here, we systematically investigate the effect of disorder and SRO on the regulation mechanism of dislocation nucleation and cross-slip in HEAs through a combination of Monte Carlo methods, molecular dynamic (MD) simulations, and theoretical analysis. Our results demonstrate that the incipient plasticity of HEAs under nanoindentation is mainly controlled by the nucleation and cross-slip of Shockley partial dislocation loops, which are found to be highly dependent on SRO. In contrast to traditional strengthening, SRO leads to a significant increase in the stable nucleation radius of the dislocation loop and cross-slip resistance. Strengthening is then achieved due to the extension of the dislocation nucleation period and the high resistance for dislocation cross-slip. Aided by the transition path analysis and theoretical model, we show that the local compositional changes originating from SRO, specifically for strong Co-Cr pairs, are the dominant factors governing the dislocation properties and accordingly, the strengthening effects. Finally, the SRO strengthen effect is further validated against different alloy systems with different SRO types. These findings suggest that the elasticity and strength of HEAs can be improved through the prolonging of the nucleation period of dislocations resulting from SRO, dictating an avenue for enhancing the mechanical properties of HEAs.
查看更多>>摘要：? 2022 Elsevier B.V.Despite significant progress has been made in the luminescent materials for white light emitting diodes (WLEDs), it is still desirable to develop novel highly efficient phosphors with appropriate excitation and high visible emission for high color rendering WLEDs. In this study, we report a novel phosphor BaGa2Si2O7:Ce3+,Tb3+ (BGSO:Ce3+,Tb3+) with highly effective green luminescence. BGSO:Ce3+,Tb3+ phosphor represents a broad excitation band in the range of 300–400 nm and intense emission at approximately 542 nm with a high photoluminescence quantum efficiency of 76.4%. The structure, luminescence, and energy transfer from the Ce3+ and Tb3+ ions were investigated in detail. Moreover, the incorporation of Na+ or K+ ions into BGSO:Ce3+,Tb3+ for charge compensation can improve the emission intensity and thermal stability. Moreover, a near ultraviolet (n-UV) pumped prototype WLED device was fabricated and it exhibited bright warm-white light with CIE chromaticity coordinates of (0.3561, 0.3344), high color-rendering index (Ra=90.4), and low CCT (3330 K) upon 20 mA driving current. This work provides a new strategy to develop high-quality solid-state LED phosphors.
查看更多>>摘要：? 2022 Elsevier B.V.The development of high-efficiency carbon-based multifunctional catalysts is of great significance for improving solid-state hydrogen storage materials. Herein, it was confirmed that CoMoO4 sheet-like nanocatalysts uniformly supported on the surface of reduced graphene oxide (CoMoO4/rGO) were successfully prepared by a simple hydrothermal reaction. The novel CoMoO4/rGO catalyst was subsequently doped into MgH2 to improve its hydrogen storage performance. MgH2–10 wt% CoMoO4/rGO starts to release hydrogen at around 204 °C, which is about 36 °C and 156 °C lower than that of MgH2 ?10 wt%CoMoO4 and pure MgH2, respectively. In addition, 6.25 wt% H2 can be released within 10 min at 300 °C. After complete dehydrogenation, H2 can be absorbed below 80 °C. Meanwhile, it can absorb 4.2 wt% H2 in 20 min under the condition of 150 °C and 3 MPa. Moreover, the activation energy of hydrogen absorption and dehydrogenation of MgH2–10 wt%CoMoO4/rGO composites are reduced by 31.44 kJ mol?1 and 33.78 kJ mol?1, respectively, compared with pure MgH2. Cycling experiment shows that the MgH2–10 wt%CoMoO4/rGO composite system can still maintain about 98% of the hydrogen storage capacity after 10 cycles. Furthermore, studies on the catalytic mechanism show that the synergistic effect between the in-situ generated MgO, Co7Mo6 and Mo may help to promote the diffusion of H2, thereby improving the MgH2 Hydrogen storage properties.
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